Answer:
Mutualistic symbiotic relationship is the relationship which exists when certain type of trees roots need a fungus in order to grow normally.
Symbiotic relations comes from the two Greek words that means "with" and "living". In a symbiotic relationship two different species lives together. The relationship may or may not be beneficial to both the species. Mutualism is a symbiotic relationship in which two species live together in order to gain benefit from each other.
The tree roots needs a fungus present in order to grow normally this can be explained by the example of mycorrhizal mutualistic relationship.
Micorrhiza is the symbiotic relationship between fungus and roots of a vascular plant. The fungus receives carbohydrates which are translocated from leaves to the root. The large surface area of the fungus mycelium helps in providing soil nutrients to the plant roots and also increases the water absorption capacity of the plant. Therefore, both the species are benefited in this association.